In some applications, ultra-wide band antennas are needed to operate at very low frequencies, for example, at or below the ultra high frequency band. At such frequencies, the electromagnetic wavelength is very large. Consequently, any antenna that is used at these frequencies will be physically very large. This physically large dimension, i.e. 30-40 feet, may result in a very high antenna that protrudes from a support object, such as a vehicle, and that can be easily seen.
An “electrically-small” antenna refers to an antenna or antenna element with relatively small geometrical dimensions compared to the wavelength of the electromagnetic fields the antenna radiates. Electrically-small antenna elements may be used in low frequency applications to overcome issues associated with the physical size of the antenna required based on the wavelength. Unfortunately, electrically small antennas tend to have relatively large radiation quality factors meaning that they tend to store, based on a time average, much more energy than they radiate resulting in very low radiation efficiencies.